In the law, the children of a son who died while his father was alive inherit up to one-third

Question:
He says: Honorable Shaykh, may Allah grant you success. You mentioned, may Allah preserve you, that the children of a son who died while his father was alive have no share in their grandfather's inheritance. In our country, there is a practice called the obligatory bequest (al-wasiyyah al-wajibah). Based on it, the children of a son who died while his father was alive inherit up to one-third, even if the grandfather did not make a bequest to them. What is the ruling on this?

Answer:
This is a law, not a Shari'ah ruling. This is not from the Shari'ah; rather, it is from the rulings of the law. Yes.